Modeling technique for large permanent magnet generators accounting for manufacturing tolerances and limitations

Wind power turbines have shown a significant increase in the energy production capabilities in recent years. For better reliability and higher efficiency, the direct drive permanent magnet (PM) generators become more desirable, particularly for off-shore wind turbines. This results in generators with large diameter and high pole pair number. To investigate the influence of manufacturing tolerances and limitations, the whole generator should be modeled and analyzed in the finite element (FE) analyses tool, but this is very time consuming process especially when multi-parameter analyses are required. Alternatively, analytical analyses may be employed, but usually with compromised accuracy. Therefore, this paper proposes a novel superposition technique based on initial FE results that are obtained from an ideal single-pole model for integer-slot and least symmetry model for fractional-slot topologies to accurately and efficiently predict the electromagnetic performance accounting for the manufacturing tolerances and limitations, the technique is validated by full FE calculations.